Pioneers in photography have always strived to create more life-like photographs. One of the difficulties of photography has been to record a three dimensional object on a two dimensional medium. In 1844, a technique for taking three dimensional, or stereoscopic, photographs was demonstrated in Germany. Two discrete images were used to create a three dimensional effect when viewed through a special device. Later, this viewing device was replaced by special glasses having different color lenses to allow the user to view black and white three dimensional pictures and movies. Special glasses having polarized lenses were later used for viewing color pictures.
The next major advance in the art was the development of a system which creates the perception of three dimensions without the need for special glasses. This revolutionary system utilizes a lenticular screen placed over a special image that presents each eye with a discrete two dimensional image. The brain combines the discrete two dimensional images to create the perception of three dimensions. To one skilled in the art, the term "lenticular print system" describes an enlarger comprising a lenticular screen having a photosensitive material either bonded to the focal plane or in contact with the focal plane. The image formed under the lenticular screen is known as a parallax-panoramogram, or as used herein, a lineiform image.
A lineiform image is comprised of zones of lines. In a conventional lenticular print system, a line of the lineiform image is a narrow image produced by a lenticular which corresponds to a discrete two dimensional image projected by an enlarger. A zone is that portion of the lineiform image which is produced by one lenticula. Thus, a zone is comprised of as many lines as the number of discrete two dimensional images projected by the enlarger. Typically, the number of discrete two dimensional images projected by the enlarger, and thus the number of lines in each zone of the lineiform image, is the same as the number of projecting apertures of the enlarger. In a conventional enlarger, there is a single projecting aperture for each lens of the enlarger, and a single discrete two dimensional image is projected by each projecting aperture.
Presently, two methods of creating suitable lineiform images are employed: direct, and indirect. In the direct method, the lineiform image is created inside a special camera equipped with a lenticular screen and is then printed using an enlarger having a single optical lens. The lineiform image thus produced is then viewed through a lenticular screen. The main problems associated with the direct method are the long photographing exposure time required and the necessity to move the camera during a single exposure.
Conversely, the indirect method utilizes a plurality of discrete two dimensional images taken from different vantage points by a camera having a corresponding plurality of optical lenses positioned on a plank and arranged in a row. This row of images is then projected through a multi-lens enlarger onto a lenticular screen to produce the lineiform image. Alignment of the lineiform image with the lenticular screen is generally not a problem. The present invention is an improvement of the prior methods and apparatus for the production of three dimensional lenticular photographs by the indirect method.
Who Before the present invention, the production of three dimensional images by the indirect method faced several problems. First, achieving an acceptable orthoscopic effect (i.e., where the scale of all three dimensions are correctly proportioned) has been difficult. Second, as composing has previously been performed in several steps, the length of time required for composing is substantial. Third, amalgamation of the discrete two dimensional images to construct the lineiform image has required excessive time and labor due to the high level of precision required. Even where amalgamation is achieved, gaps between the zones of the lineiform image or gaps between the individual lines of the lineiform image, or both, were unavoidable. Fourth, three dimensional photographs produced according to past teachings have a limited viewing window in which the optimal three dimensional effect is perceived. Finally, prior three dimensional photographs suffer from a stroboscopic effect whereby the viewer perceives two separate images simultaneously, or perceives a distinct switch from an image produced by one lens to an image produced by another lens as the viewer moves his head.
The prior advancements relating to three dimensional imaging using a lenticular screen are based on the theoretical supposition that superior quality can be achieved by forcing each zone of the lineiform image to occupy the exact width of the space under a lenticula. In practice, this requires that the aperture angle of each lenticula be effectively filled with the projecting apertures of the enlarger. The aperture angle is that angle which is formed by passing rays originating from the point at which perpendicular projections of the edges of the lenticula meet the focal plane through the optical center of the lenticula. FIG. 4 of U.S. Pat. No. 3,953,869 to Wah Lo, for example, shows four discrete two dimensional images projected onto the lenticular screen and producing four discrete, non-overlapping lines of the lineiform image under a lenticula. Similarly, FIG. 9 of U.S. Pat. No. 3,895,867 to Lo shows six discrete, non-overlapping lines produced on the lineiform image. In order for each zone of the lineiform image to occupy the exact width of the space under a lenticula, each line of the lineiform image can be no wider than w/n; where w is the width of each lenticula, and n is the number of discrete images projected onto the lenticular screen. Most methods for achieving this goal require printing the lineiform image in several exposures while adjusting the position of the lenticular screen relative to the enlarger between each exposure to ensure that the lines are congruent.
The objective of the prior indirect methods and apparatus has been to provide each of the viewer's eyes with a separate image so that the viewer's left eye sees one discrete image and the viewer's right eye sees another discrete image. If there are ten (10) discrete two dimensional images projected onto the lenticular screen by the enlarger, and thus ten (10) lines of the lineiform image projected onto the focal plane in each zone of the lineiform image, the viewer may see, for example, the 3rd image with the left eye and the 6th image with the right eye from one position. From a different position, the viewer might see, for example, the 4th image with the left eye and the 7th image with the right eye. In addition, the prior indirect methods avoid overlapping of the lines of the lineiform image.
The objective of the indirect method and apparatus of the invention, on the other hand, is to provide each of the viewer's eyes with at least two, and preferably more, overlapping discrete images. If there are forty (40) two dimensional images projected onto the lenticular screen by the enlarger, and thus forty (40) lines of the lineiform image projected onto the focal plane in each zone of the lineiform image, the viewer may see, for example, the overlapping 19th, 20th, 21st and 22nd images with the left eye and the overlapping 23rd, 24th, 25th and 26th images with the right eye from one position. From a different position, the viewer might see, for example, the overlapping 20th, 21st, 22nd and 23rd images with the left eye and the overlapping 24th, 25th, 26th and 27th images with the right eye. The multiple, overlapping two dimensional images viewed on the lineiform image are not perceived to be blurred by the viewer because the difference in parallax between the adjacent overlapping images presented to each eye is less than the resolution capability of the viewer. Furthermore, the overlapping two dimensional images are arranged and aligned on the lineiform image so that the perceived location of the elements in objective space reproduced on the lineiform image do not change location relative to the lenticular screen when the perspective of the viewer is changed.
The prior methods of viewing just two separate images create a sharp three dimensional image in only a limited viewing area. When the viewer's head moves to a position from which the viewer views the edges of two adjacent lines of the lineiform image, the viewer will see an image wherein each eye perceives two separate images simultaneously. This phenomenon is known as "stroboscopic effect." In other words, the viewer will see, for example, the 3rd and 4th images with the left eye, and the 6th and 7th images with the right eye because of the large parallax between adjacent two dimensional images. These two images are sufficiently different so that there is a perception of two superimposed discrete images. In the prior apparatus, the projecting apertures of the enlarger are positioned closer to the lenticular screen than the distance limit described herein, and are required to be positioned in edge-to-edge relationship, or are required to move relative to the lenticular screen to simulate edge-to-edge relationship. The total number of projecting apertures used by the prior apparatus, however, is insufficient to produce a small enough parallax between adjacent two dimensional images so that the discrete images are perceived to be a solid object.
In the method of the invention, viewing, for example, four images simultaneously with each eye eliminates stroboscopic effect. The greater number of discrete two dimensional images divides the largest single parallax into such small parts that the four discrete two dimensional images are perceived to be a solid object. The method of the invention further provides empirical techniques for: 1) determining the optimal number of two dimensional images to use; and 2) determining the minimum number of two dimensional images necessary to eliminate stroboscopic effect.
The prior indirect methods also presume that the projecting distance of the enlarger should be the same as the viewing distance of the three dimensional photograph. When viewing the three dimensional photograph from the projecting distance, the positions of the viewer's left and right eyes must exactly match the positions of two of the projecting apertures. This requirement limits the number of projecting apertures that can be used. When the viewing distance is changed, the left and right eyes of the viewer no longer match the positions of any two of the projecting apertures. Accordingly, from any distance except the projecting distance, the viewer will perceive stroboscopic effect in some area of the three dimensional photograph. Also, as the viewer moves away from the lenticular screen, the perceived image will deepen (i.e., the perceived image will not maintain orthoscopic accuracy in the depth dimension). Conversely, as the viewer moves towards the lenticular screen, the perceived image will flatten. In the method of the invention, matching the viewer's eyes with the positions of the projecting apertures is not required. The viewer may view the lenticular photograph at viewing distances different from the projecting distance. Thus, stroboscopic effect is eliminated in all areas of the three dimensional photograph.
The prior methods and apparatus are plagued by a further consequence resulting from positioning the projecting apertures closer to the lenticular screen than the "distance limit" defined hereinafter. Simply eliminating the gaps between lines of the lineiform image does not permit the prior methods and apparatus to accomplish both one-step imaging and one-step printing without moving at least one of the following components of the lenticular print system: 1) the film; 2) the lenticular screen; 3) the projecting apertures; or 4) the photosensitive material. If the two dimensional images are created by a single exposure of the camera, then either multiple exposures of the enlarger are required to print the three dimensional photograph or at least one of the elements of the lenticular print system must be moved during a single exposure of the enlarger. If the two dimensional images are printed by one exposure of the enlarger and without moving at least one of the above elements of the lenticular print system, then the two dimensional images must be created by multiple exposures of the camera or by moving at least one element of the imaging system during a single exposure of the camera. In the invention, creating two dimensional images with the camera, and printing three dimensional images with the enlarger does not require multiple exposures of the imaging system or the lenticular print system, or moving elements of the imaging system or the lenticular print system.